The present invention relates to a device for attaching compensation weights with an adhesive layer to an attachment surface of a rotatable component such as a vehicle wheel, for purposes of unbalance compensation. The device has holding structure with two holding parts to secure a compensation weight to the vehicle wheel. A pressing element between the holding parts is pressed onto a rear surface of the compensation weight opposite from the adhesive layer. A guide directs the holding structure to the unbalance compensation site of the attachment surface where the compensation weight is pressed onto the rotatable component.
In a device of this nature, in EP 0,681,169 B1, a compensation weightxe2x80x94with its edge that lies on the side bearing the adhesive layerxe2x80x94is placed onto the attachment surface by a guide. Subsequently, via a pressure transmission configured as a bolt, pressure is exerted onto the compensation weight against the attachment surface. As a result, the compensation weight swivels around the edge and is pressed with its adhesive surface onto the attachment surface. The pressure on the compensation weight may be exerted by an automatic actuation device, for example, an electric lifting magnet. This known device is only suitable for compensation weights having a relatively compact shape, since the contact pressure is transferred to the compensation weight at only one point.
DE 4,440,812 C2 discloses a device for gluing balancing weights onto shafts, which consists of pressing structure essentially having a basic element with an elastic, height-adjustable receptacle for the balancing weight. Underneath, guide bars pivot from the shaft mid-point to the shaft circumference, and between the guide bars and below the elastic receptacle, a height-adjustable molded shell is provided for pressing the balance weights. This device is only suitable for convex attachment surfaces.
The present invention is based upon the objective of creating a device of the type described above, which allows the automatic attachment of self-adhesive compensation weights having different and also sizable lengths, particularly to concave attachment surfaces.
According to the present invention, a pressing element has a pressing surface capable of being deformed as a function of pressing force. The rear surface of a compensation weight lies on the pressing surface. The pressing surface in the unstressed basic position of the pressing element has such a shape so that the pressing force is transferred to the middle section of the compensation weight, and as the pressing force increases, the pressing surface is deformed in such a way that the pressing force is also transferred onto the ends of the compensation weight.
With the device of the present invention it is possible to press a self-adhesive compensation weight onto the attachment surface of a component to be balanced in such a way that the compensation weight is first pressed in the middle and from there, it is progressively pressed towards the two ends in the circumferential direction of the component. As a result, the inclusion of air bubbles between the adhesive layer and the component is avoided, and a secure adhesion of the compensation weight is ensured. The device according to the invention also has the advantage that, within certain limits, it can automatically adapt to different radii of curvature of the attachment surfaces to which the compensation weights are applied. As the pressing force increases, the curvature of the pressing surface of the pressing element adapts to the curvature of the compensation weight that is being pressed against the attachment surface. In the longitudinal direction of the holding parts, the pressing surface can have a relatively sizable length, so that even very long compensation weights can be reliably pressed over their entire length.
In an advantageous embodiment of the device according to the invention, the pressing element consists of a leaf spring that has, on both of its ends, oppositely bent sections attached to one part of the holding means and, with its middle section, the leaf spring forms the pressing surface. This embodiment can be simply and inexpensively manufactured. It also has the advantage that, as the pressing force increases, it is distributed from the middle section over the entire length of the compensation weight and thus, even with sizable lengths, a uniform pressing of the compensation weight is obtained.
According to another proposal of the invention, the pressing element consists of two leaf spring arms that are separate from each other and that extend symmetrically in opposite directions from a middle plane of the device. The opposing ends are rigidly attached to a part of the holding structure. In this embodiment, one end of a leaf spring arm is preferably provided with a tongue that engages a recess in the end of the other leaf spring arm. This serves to bridge the joint between the leaf spring arms. In comparison to a one-part leaf spring, the leaf spring arms have less spring stiffness. As a result, they allow a shift in the point of action of the pressing force toward the area of the ends of a compensation weight, even when relatively weak forces are involved. The free end areas of the flexible leaf spring arms that form the pressing surface may also be configured so as to be thickened. This increases their dimensional stiffness, and they retain a predefined curvature, even under the load of the pressing force. In operation, the leaf spring arms produce a type of rolling motion on the rear surface of the compensation weight. In order to limit the elastic deformability of the leaf spring and of the leaf spring arms, adjustable stops may be mounted on the holding structure.
In order to limit the pressing force exerted by the guide structure, in another embodiment of the invention, the device is provided with a transducer that detects the elastic deformation of the pressing element. Once a predefined setpoint is reached, the pressing motion of the guide means is terminated and, after the holding parts are detached, the device is moved back into a starting position for the attachment of a new compensation weight. An example of a suitable transducer is a proximity switch, for example, positioned on a carrier part of the holding structure that responds to a certain approximation of the pressing element.
In another embodiment of the invention, in order to secure the compensation weight on the deformable part of the pressing element, the holding parts arranged on both sides of the pressing element are guided in such a way that they follow the positional change of the deformable part. Therefore, the holding parts can hold the compensation weight until the pressing procedure has been completed and this is accomplished without impairing deformation of the pressing element. Preferably, the holding parts are supported in the linear guides of a clamping mechanism attached to the pressing element.